Key structure

ABSTRACT

A key structure includes a key cap, a supporting board, a bridge assembly, a first supporting part, a second supporting part, an attractable element and a magnet. The bridge assembly includes first and second hinge parts. The first hinge part has a first pivot coupling portion. The second hinge part has a second pivot coupling portion. The first and second supporting parts are coupled to two ends of the first and second pivot coupling portions, respectively, wherein the first and the second supporting parts are disposed on the supporting board, a material of the first supporting part is different from a material of the supporting board, and a material of the second supporting part is different from the material of the supporting board. The attractable element is disposed on the second hinge part. The magnet is correspondingly located under the attractable element.

This application is a continuation-in-part application of U.S.application Ser. No. 15/618,602, filed on Jun. 9, 2017, which is acontinuation-in-part application of U.S. application Ser. No.15/049,001, filed on Feb. 19, 2016, which claims the benefit of U.S.provisional application Ser. No. 62/158,526, filed on May 7, 2015, andthe benefit of Taiwan application Serial No. 104133859, filed on Oct.15, 2015. These related applications are incorporated herein byreferences.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates in general to a key structure, and moreparticularly to a key structure with lightweight and thinning design.

Description of the Related Art

In a conventional key structure, an elastic member provides a recoveryelastic force for a key cap supported by a scissor structure to restorethe key cap to its pre-pressing position. However, the scissorstructure, being hard to assemble and having a longer pressing stroke,is not suitable to the keyboard with thinning design. Meanwhile, whenthe key cap is pressed, the downward force is transmitted to a thin filmcircuit board formed of bi-layer circuits by the elastic member.However, if the downward force is insufficient, it is difficult to makethe bi-layer circuits come into contact, and the sensitivity will bepoor. Besides, the key structure cannot be stored to reduce thestructural height when the key structure is not in use. Under thecurrent trend of ultra-thinning design of the portable computer, thereis a strong need to develop a new key structure whose overall height isreduced when the portable computer is closed.

SUMMARY OF THE INVENTION

The invention is directed to a key structure with lightweight andthinning design, capable of shortening the pressing stroke andincreasing the sensitivity.

According to one embodiment of the present invention, a key structureincluding a key cap, a supporting board, a bridge assembly, a firstsupporting part, a second supporting part, an attractable element and amagnet is provided. The bridge assembly is disposed between the key capand the supporting board. The bridge assembly includes a first hingepart and a second hinge part. The first hinge part has a first pivotcoupling portion. The second hinge part has a second pivot couplingportion. The first and second supporting parts are coupled to two endsof the first pivot coupling portion and two ends of the second pivotcoupling portion, respectively, wherein the first supporting part andthe second supporting part are disposed on the supporting board, amaterial of the first supporting part is different from a material ofthe supporting board, and a material of the second supporting part isdifferent from the material of the supporting board. The attractableelement is disposed on the second hinge part. The magnet iscorrespondingly located under the attractable element.

The above and other aspects of the invention will become betterunderstood with regard to the following detailed description of thepreferred but non-limiting embodiment(s). The following description ismade with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-2 are a top-view decomposition diagram and a bottom-viewdecomposition diagram of a key structure according to an embodiment ofthe invention respectively.

FIG. 3 is a decomposition diagram of a key structure before assemblyaccording to an embodiment of the invention.

FIG. 3-1 is a schematic diagram of a base board with a magnet.

FIG. 3-2 is a schematic diagram of a receiving slot for receiving amagnet.

FIG. 4 is a schematic diagram of a key structure after assemblyaccording to an embodiment of the invention.

FIGS. 5A and 5B are appearance diagrams of the key structure of FIG. 4in a releasing status and a storing status respectively.

FIGS. 6A and 6B are cross-sectional views of a key structure along anA-A cross-sectional line of FIG. 5A when the key structure is pressed tochange to a pressing status from a releasing status.

FIG. 7A is a top-view diagram of a key structure according to anotherembodiment of the invention.

FIG. 7B is a cross-sectional view of a key structure along a B-Bsectional line of FIG. 7A, and FIG. 7B-1 is an enlarged portion at themagnet.

FIG. 7C is a cross-sectional view of a key structure along a C-Csectional line of FIG. 7A, and FIG. 7C-1 is an enlarged portion at themagnet.

FIGS. 8A and 8B are schematic diagrams of a key structure according toanother embodiment of the invention when the key structure is pressed tochange to a pressing status from a releasing status.

FIG. 8C is a schematic diagram of a pivot structure of a key structureaccording to another embodiment of the invention.

FIG. 9A is a schematic diagram of a key structure according to anotherembodiment of the invention.

FIG. 9B is a top-view diagram of a key structure of FIG. 9A and anenlarged portion at the first pivot coupling portion.

FIGS. 10A and 10B are schematic diagrams of a key structure according toanother embodiment of the invention when the key structure is pressed tochange to a pressing status from a releasing status.

FIG. 11A is a top-view diagram of the thin film circuit board, and FIG.11B is a top-view diagram of a first hinge part and a second hinge partdisposed on the thin film circuit board.

DETAILED DESCRIPTION OF THE INVENTION

A number of embodiments are disclosed below for elaborating theinvention. However, the embodiments of the invention are for detaileddescriptions only, not for limiting the scope of protection of theinvention.

FIGS. 1-2 respectively are a top-view decomposition diagram and abottom-view decomposition diagram of a key structure 2 according to anembodiment of the invention. Refer to FIG. 1. The key structure 2includes a key cap 10 and a bridge assembly 20. The bridge assembly 20is disposed under the key cap 10. The bridge assembly 20 includes afirst hinge part 21 and a second hinge part 22 intersecting to form aV-shaped structure. One end of the first hinge part 21 has a first linkbar 211, and the other end of the first hinge part 21 has a first pivotcoupling portion 212 and a first shaft X1. One end of the second hingepart 22 has a second link bar 221, and the other end of the second hingepart 22 has a second pivot coupling portion 222 and a second shaft X2.Additionally, the first shaft X1 of the first hinge part 21 has a firstconnecting portion 213, and the second shaft X2 of the second hinge part22 has a second connecting portion 223. The first connecting portion 213and the second connecting portion 223 are coupled to each other throughsuch as a protrusion portion and an indention portion to form an axis A1(refer to FIG. 4, FIG. 6A and FIG. 6B), so that the first shaft X1 ofthe first hinge part 21 and the second shaft X2 of the second hinge part22 are on the same axis.

As indicated in FIG. 1, the key structure 2 further includes anattractable element 25 and a magnet 26. The attractable element 25 isdisposed under the bridge assembly. In an embodiment, the attractableelement 25 can be fixed under the bridge assembly through an engagingstructure. In another embodiment, the bridge assembly 20 is made byusing an in-mold injection method. First, the attractable element 25 isdisposed inside a mold, and then plastics is heated and injected intothe mold to form the first hinge part 21 and the second hinge part 22 ofthe bridge assembly 20, so that the first hinge part 21 or the secondhinge part 22 formed by way of injection can be integrally formed in onepiece with the attractable element 25 disposed inside the mold. Theattractable element 25 and the magnet 26 can be deemed as a magneticassembly. The magnet 26 is preferably made of permanent magneticmaterials, which includes hard ferrites magnet and rare-earth Nd—Fe—BMagnet. Hard ferrites magnet is made of Sro, or Bao and Fe2O3 by ceramicmanufacturing technology. Rare-earth Nd—Fe—B Magnet is mainly made ofneodymium (Nd), iron (Fe), and boron (B) by method of metal melting andpowder metallurgy, to be sintered with A1-Ni—Co, samarium (Sm)—Ni—Co,Sm—Co.

Refer to FIG. 2. In an embodiment, the attractable element 25 has afirst end 251 and a second end 252. The first end 251 corresponds to afirst attractive position P1, and the second end 252 corresponds to asecond attractive position P2. Additionally, the magnet 26 provides amagnetic force and is movable between the underneath of the firstattractive position P1 and the second attractive position P2. When thefirst end 251 of the attractable element 25 is attracted by the magneticforce and generates a reaction force to the bridge assembly 20, thefirst end 251 of the attractable element 25 is moved to the firstattractive position P1 with respect to the axis A1 (refer to FIG. 4,FIG. 6A and FIG. 6B), so that the first hinge part 21 and the secondhinge part 22 can be activated through the reaction force (that is areleasing status as indicated in FIG. 6A). Besides, when the second end252 of the attractable element 25 is attracted by a magnetic force andgenerates a reaction force to the bridge assembly 20, the second end 252of the attractable element 25 is moved to the second attractive positionP2 with respect to the axis A1, so that the first hinge part 21 and thesecond hinge part 22 can be activated through the reaction force.Therefore, by changing the attraction between the magnet 26 and thefirst end 251 or the attraction between the magnet 26 and the second end252 of the attractable element 25 to move the first hinge part 21 andthe second hinge part 22, the bridge assembly 20 of the presentembodiment can be switched between the releasing status and the storingstatus. In another embodiment, the magnet 26 can be fixed on a positionunder the first end 251 of the attractable element 25, so that the firsthinge part 21 and the second hinge part 22 of the bridge assembly 20 canbe switched between the releasing status and the pressing status.

In an embodiment, the attractable element 25 can be formed of aferromagnetic material, and the magnet 26 can be formed of a permanentmagnet or an electromagnet.

Refer to FIG. 2. In an embodiment, the key cap 10 includes a pluralityof link bar supporting portions 102 on the bottom of key cap 10 forfixing or slidably supporting the first link bar 211 of the first hingepart 21 and the second link bar 221 of the second hinge part 22. In anembodiment, a first actuation portion 214 is protruded and disposed atthe part in the outer side of the first hinge part 21 near the firstlink bar 211. The first actuation portion 214 is correspondingly locatedabove a touch portion 32, such that when the key cap 10 is pressed, thefirst actuation portion 214 can touch the touch portion 32 to generate akey pressing signal. In another embodiment, a second actuation portion224 is protruded and disposed at the part in the outer side of thesecond hinge part 22 near the second link bar 221. The second actuationportion 224 is correspondingly located above another touch portion 32,such that when the key cap 10 is pressed, the second actuation portion224 can contact the other touch portion 32 to generate a key pressingsignal. In other words, the key structure 2 of the invention has atleast one actuation portion contacting at least one touch portion 32 togenerate a key pressing signal.

Refer to FIG. 3, a decomposition diagram of a key structure 2A beforeassembly according to an embodiment of the invention is shown. In anembodiment, the key structure 2A further includes a thin film circuitboard 30, a supporting board 40 and a base board 50. The thin filmcircuit board 30 can be disposed on the supporting board 40 orintegrally formed in one piece with the supporting board 40. In anembodiment, the supporting board 40 is disposed on the base board 50 andcan slide with respect to the base board 50.

Refer to FIG. 3. In an embodiment, the touch portion 32 is disposed onthe film circuit board 30 and corresponds to a position of a switchelement 31 of the thin film circuit board 30. When the touch portion 32is pressed, the switch element 31 disposed under the touch portion 32 isactivated to generate a key pressing signal. The key pressing signal canbe transmitted to a position processor (not illustrated) via the circuitof the film circuit board 30. Then, the position processor calculatesthe coordinate position of the key and generates a key pressinginstruction corresponding to the key. In another embodiment, as shown inFIG. 10B the first actuation portion 214′ and the second actuationportion 224′ may press two switch elements 31 of the thin film circuitboard 30 directly to generate a pressing signal.

In an embodiment, the touch portion 32 can be formed of an elasticmaterial such as rubber, epoxy resin, semi-cured colloid or plastics inthe shape of a dome.

In an embodiment, the switch element 31 includes an upper conductivelayer and a lower conductive layer (not illustrated), which areseparated by a gap. When the touch portion 32 is pressed, the upperconductive layer and the lower conductive layer contact each other togenerate a key pressing signal.

Refer to FIG. 3. The supporting board 40 includes a first supportingpart 41 and a second supporting part 42 which are opposite to each otherand erected on the supporting side 401. The first supporting part 41includes two first pivot holes 411 and 412, and the second supportingpart 42 includes two second pivot holes 421 and 422. The first pivotholes 411 and 412 and the second pivot holes 421 and 422 are disposedoppositely for receiving two ends of the first pivot coupling portion212 and two ends of the second pivot coupling portion 222, respectively.In an embodiment, the two ends of the first pivot coupling portion 212of the first hinge part 21 can be located at the first pivot hole 411and the second pivot hole 421, respectively; the two ends of the secondpivot coupling portion 222 of the second hinge part 22 can be located atthe other first pivot hole 412 and the other second pivot hole 422,respectively. Thus, the key cap 10 can be assembled onto the supportingboard 40 through the bridge assembly 20 and can move upward/downwardwith respect to the supporting board 40. The movement of the first pivotcoupling portion 212 and the second pivot coupling portion 222 can beobtained with reference to the descriptions of FIGS. 8A and 8B. In thepresent embodiment, the supporting board 40 is a metal board, and thefirst supporting part 41 and the second supporting part 42 are plasticmaterial disposed on the supporting board 40. In other words, thematerial of the first supporting part 41 is different from the materialof the supporting board 40, and the material of the second supportingpart 42 is different from the material of the supporting board 40.

Referring to FIG. 3, the base board 50 can be a metal board or areinforced plastic substrate. The base board 50 is disposed under thesupporting board 40 to reinforce the rigid structure of the supportingboard 40. In other words, the base board 50 can be used as a base of thekeyboard, and there is no need to additionally dispose a board on thebase of the keyboard, hence reducing the weight and cost of thekeyboard. In another embodiment, when the supporting board 40 hassufficient rigidity, the supporting board 40 can also be used as a baseof the keyboard and there is no need to additionally dispose the baseboard 50 under the supporting board 40.

Refer to FIG. 3. In an embodiment, the supporting board 40 has a firstopening 43, and the base board 50 has a second opening 51. The firstopening 43 and the second opening 51 are basically located under theattractable element 25 and are capable of receiving the magnet 26. Thesecond opening 51 can fix the magnet 26 on the base board 50. The sizeof the first opening 43 is, for example, equal to or larger than that ofthe second opening 51.

Refer to FIG. 3-1. In an embodiment, the base board 50 has a recess 51′for receiving the magnet 26 of each key structure on the base board 50.The recess 51′ does not pass through the base board 50 and has anopening facing upward. Refer to FIG. 3-2, when the magnet 26 is disposedin the recess 51′, the bottom of the magnet 26 is in contact with thebase board 50 and is encompassed by sidewalls of the recess 51′.Therefore, a magnetic field of the magnet 26 forms a closed loop toenhance the intensity of the magnetic force.

FIG. 4 is a schematic diagram of a key structure 2A after assemblyaccording to an embodiment of the invention. Refer to FIG. 4. In anembodiment, the first hinge part 21 and the second hinge part 22 areassembled onto the supporting board 40 through the first supporting part41 and the second supporting part 42, respectively. After assembly, thefirst hinge part 21 and the second hinge part 22 are connected as onepiece and the rotation center is located on the axis A1. Refer to FIGS.1 and 4. Since the first shaft X1 and the first pivot coupling portion212 are not coaxial and the second shaft X2 and the second pivotcoupling portion 222 are not coaxial either, the first pivot couplingportion 212, the second pivot coupling portion 222 and the axis A1 usedas the rotation center form three non-coaxial hinge points (such as inthe shape of W). Therefore, after assembly, the first hinge part 21 andthe second hinge part 22 basically form a W-shaped structure.

FIG. 5A is an appearance diagram of the key structure 2A of FIG. 4 in areleasing status. FIGS. 6A and 6B are cross-sectional views of a keystructure 2A along an A-A cross-sectional line of FIG. 5A changed to apressing status from a releasing status. Refer to FIG. 6A. In anembodiment, when the key cap 10 is not pressed, the first end 251 of theattractable element 25 is attracted by the magnet 26 and fixed at thefirst attractive position P1, so that the key cap 10 and the bridgeassembly 20 enter a releasing status. Refer to FIG. 6B. When the key cap10 is pressed, the first end 251 of the attractable element 25 is drivento move away from the magnet 26, so that the key cap 10 is moved to apressing position from a releasing position. Then, when the key cap 10is released, the first end 251 of the attractable element 25 is againattracted by the magnet 26, so that the key cap 10 and the bridgeassembly 20 are driven to the releasing position by the magnetic force.Therefore, when the user presses or releases the key structure 2A, thekey structure 2A is moved upward and downward between a pressingposition and a releasing position by the magnetic force.

Refer to FIG. 5B. In an embodiment, the base board 50, such as a slidingboard, slides with respect to the supporting board 40 along a firstsliding direction S1, so that the key structure 2A′ enters a storingstatus. Alternatively, the supporting board 40, such as a sliding board,slides with respect to the base board 50 along a second slidingdirection S2, so that the key structure 2A′ enters a storing status.When the key cap 10 is moved to the storing position, the receivingspace that the key structure 2A′ requires will be relatively reduced,and the overall height of the key structure 2A′ will be reducedaccordingly. Such condition makes the key structure having a lowerheight, so that it is benefited the storage of keyboard. For example, akeyboard of laptop computer with a lower height, and the screen can befolded upon the keyboard. Laptop computer can become slimmer than aconventional laptop computer.

In an embodiment, the first end 251 of the attractable element 25 canhave a face contact or a line contact with the magnet 26. When the toucharea is greater, the magnetic force would become greater, and theattractable element 25 would move downward and impact fast on the magnetto generate beating noise. Further, if the touch area between theattractable element 25 and the magnet 26 is changed, the variant of themagnetic force would be occurred to make the magnetic force unstable.

Referring to FIG. 7A, FIG. 7B and FIG. 7B-1, FIG. 7A is a top-viewdiagram of a key structure 2B (the key cap 10 is indicated by a dottedline) according to another embodiment of the invention, and FIGS. 7B and7B-1 are a cross-sectional view of a key structure 2B along a B-Bsectional line of FIG. 7A and an enlarged portion at the magnet 26. Themagnet 26 has an upper surface 261, and the attractable element 25 has amiddle portion 253 between the first end 251 and the second end 252. Themiddle portion 253 of the attractable element 25 has a lower surface2531 facing the upper surface 261 in parallel and the lower surface 2531separates a gap P from the upper surface 261, such as 0.5 mm. The firstend 251 of the attractable element 25 has a lower surface 2511 facingthe upper surface 261 and the lower surface 2511 contacts the uppersurface 261 at an acute angle. The lower surface 2511 forms an obtuseangle with the lower surface 2531, and the obtuse angle is such as about170-175 degrees. That is, the lower surface 2511 of the first end 251forms an inclined angle with the upper surface 261, and the inclinedangle θ₁ is such as about 5-10 degrees. The attractable element 25 has aline contact with the magnet 26, so that the magnetic force is reducedto make the key structure 2B easy to be pressed. Meanwhile, line contactcan make the variant of the magnetic force reduced and make the magneticforce stable, and the beating noise would be reduced. Further, in theFIG. 5B, when the base board 50 slides with respect to the supportingpart 40, line contact also can reduce the pushing force or pulling forceapplied to the base board 50.

In addition, as shown in FIG. 7B, the attractable element 25 has anopening 254, and the opening 254 overlaps the upper surface 261 of themagnet 26 in a vertical projecting direction of the key cap 10. When thesize of the opening increases, the overlapping area of the attractableelement 25 and the upper surface 261 of the magnet 26 is reduced so asto reduce the magnetic force.

Moreover, referring to FIG. 7A, FIG. 7C and FIG. 7C-1, FIG. 7C and FIG.7C-1 are a cross-sectional view of a key structure 2B along a C-Csectional line of FIG. 7A and an enlarged portion at the magnet 26. Theattractable element 25 further includes a tongue plate 255 extendinginto the opening 254, and a lower surface 2551 of the tongue plate 255extends towards the upper surface 261 and forms an inclined angle θ₂with the upper surface 261, and the inclined angle θ₂ is such as about5-10 degrees. That is, the tongue plate 255 is in line contact with theupper surface 261 of the magnet 26 so as to compensate the magneticforce reduced due to the opening 254. Meanwhile, the tongue plate 255also can be attracted on the upper surface 261 of the magnet 26 toincrease the positioning between the attractable element 25 and themagnet 26.

Referring to FIG. 8A and FIG. 8B, FIGS. 8A and 8B are schematic diagramsof a key structure 2C according to another embodiment of the inventionwhen the key structure 2C is pressed to change to a pressing status froma releasing status. When the key cap 10 is pressed, the axis A1 as therotation center is moved upward such that the first pivot couplingportion 212 and the second pivot coupling portion 222 are moved towardsthe insides of two first pivot holes 411 and 412 and contact the insidesof the two first pivot holes 411 and 412. When the key cap 10 isreleased, the axis A1 as the rotation center is moved downward, suchthat the first pivot coupling portion 212 and the second pivot couplingportion 222 respectively move towards the outsides of two first pivotholes 411 and 412 of the first hinge part 41 and contact the outsides ofthe two first pivot holes 411 and 412. Therefore, the axis A1 can moveupward or downward.

As illustrated in FIG. 8A and FIG. 8B, except from the two first pivotholes 411 and 412, the first supporting part 41 further includes apositioning hole 413. The positioning hole 413 is located between thetwo first pivot holes 411 and 412 and separated from the two first pivotholes 411 and 412. In addition, the first hinge part 21 has at least apositioning stick 216 on the axis A1 and received in the positioninghole 413. When the key cap 10 is pressed to move downwards, thepositioning stick 216 has a degree of freedom with respect to thepositioning hole 413 in a movement direction of the key cap 10 to limitthe movement of the positioning stick 216. Therefore, the position ofthe attractable element 25 corresponding to the magnet 26 can be securedby the positioning hole 413 and the positioning column 216 of thepresent embodiment to make the magnetic force more stable. In anembodiment, the use of a single positioning stick 216 can make theopposite sides of the first hinge part 21 asymmetrically, so that thepositions of the first hinge part 21 and the second hinge part 22 atcorresponding first pivot holes 411 and 412 can be easily determinedaccording to the positioning stick 216 to achieve the fool-proof effect.In another embodiment (not shown), the positioning stick also can bedisposed on the second hinge part when the first hinge part and thesecond hinge part are exchanged.

Further, referring to FIG. 8C, in an embodiment, the fits between thetwo ends of the second pivot coupling portion 222 and the correspondingfirst pivot hole 412′ and second pivot hole (not illustrated in FIG. 8C)can adopt close clearance to reduce the tolerance and avoid the secondpivot coupling portion 222 moving laterally, such that the position ofthe attractable element 25 corresponding to the magnet 26 can be securedto make the magnetic force more stable. On the other hand, the fitsbetween the two ends of the first pivot coupling portion 212 and thecorresponding first pivot hole 411′ and second pivot hole (notillustrated in FIG. 8C) can adopt loose clearance to increase thetolerance such that the first pivot coupling portion 212 can movelaterally, however, since the attractable element 25 is not located onthe first hinge part 21, the position of the attractable element 25corresponding to the magnet 26 would not be shifted.

Next, referring to FIG. 9A and FIG. 9B, FIG. 9A is a schematic diagramof a key structure 2D (the key cap 10 and the supporting parts 41, 42are indicated by dotted lines) according to another embodiment of theinvention, and FIG. 9B is a top-view diagram of a key structure 2D ofFIG. 9A and an enlarged portion at the first gasket 217. The keystructure 2D further includes two first gaskets 217 (only shown one) andtwo second gaskets 227 (only shown one). The first gaskets 217 aredisposed on two ends of the first pivot coupling portion 212respectively so that the first hinge part 21 and the first supportingpart 41 as well as the first hinge part 21 and the second supportingpart 42 are spaced apart at a first distance S1, respectively. Inaddition, the second gaskets 227 are disposed on two ends of the secondpivot coupling portion 222 so that the second hinge part 22 and thefirst supporting part 41 as well as the second hinge part 22 and thesecond supporting part 42 are spaced apart at a second distance (notshown), respectively. The second distance is substantially equal to thefirst distance S1. Therefore, the friction force is reduced since thedirect contacts between the two lateral sides 215 of the first pivotpart 21 and the corresponding first supporting part 41 and secondsupporting part 42 are avoided. Thus, the first hinge part 21 is easy torotate accordingly. On the other hand, the friction force is reducedsince the direct contacts between the two lateral sides 225 of thesecond pivot part 22 and the corresponding first supporting part 41 andsecond supporting part 42 are avoided. Thus, the second hinge part 22 iseasy to rotate accordingly.

Referring to FIG. 10A and FIG. 10B, FIGS. 10A and 10B are schematicdiagrams of a key structure 2E according to another embodiment of theinvention when the key structure 2E is pressed to change to a pressingstatus from a releasing status. In an embodiment, a first protrusion 218and a second protrusion 228 are disposed on positions where the firsthinge part 21 and the second hinge part 22 contact with the thin filmcircuit board 30 respectively. The first protrusion 218 has a height(greater than 0) protruded from a bottom side of the first hinge part 21and the second protrusion 228 has a height (greater than 0) protrudedfrom a bottom side of the second hinge part 22. Therefore, when thefirst hinge part 21 and the second hinge part 22 rotate to each other,the first protrusion 218 interferes with the thin film circuit board 30and the second protrusion 228 interferes with the thin film circuitboard 30, so that the first protrusion 218 and the second protrusion 228can be used to reduce a tolerance between the first hinge part 21 andthin film circuit board 30 and a tolerance between the second hinge part22 and thin film circuit board 30, and thereby a noise generated bypressing the key structure 2E in the existence of the tolerance can beavoided.

Please refer to FIG. 10B. When the key cap 10 moves downwards, the firstactuation portion 214′ and the second actuation portion 224′ may presstwo switch elements 31 of the thin film circuit board 30 directly togenerate a pressing signal. When the two switch elements 31 are pressed,the two switch elements 31 can recess into two cavities 44 of thesupporting board 40 respectively. The amount of the switch elements 31is not limited to two, also can be more than two.

Referring to FIGS. 10A-10B and FIG. 11A-11B, FIG. 11A is a top-viewdiagram of the thin film circuit board 30, and FIG. 11B is a top-viewdiagram of a key structure 2F with a first hinge part 21 and a secondhinge part 22 disposed on the thin film circuit board 30. In anembodiment, the thin film circuit board 30 has two first switch elements31′ and two second switch elements 31″ for each key cap 10, and thefirst hinge part 21 has two first actuation portions 214′correspondingly located above the two first switch elements 31′, and thesecond hinge part 22 has two second actuation portions 224′correspondingly located above the two second switch elements 31″. Thefirst actuation portions 214′ and the second actuation portions 224″ areadjacent to two edges of the key cap 10 and on opposite sides withrespect to the axis A1 passing through the center of the key cap 10. Inother words, the positions where the first hinge part 21 and the secondhinge part 22 contact with the thin film circuit board 30 are adjacentto the four corners of the key cap 10. Accordingly, no matter the middleor edges of the key cap 10 is pressed by the user, a correspondingsignal can be easily triggered so as to increase the sensitivity of thekey structure 2F. The first switch elements 31′ and the second switchelements 31″ may be conducted in series in the thin film circuit board30 of the present embodiment, so that a pressing signal is generatedwhen just one of the switch elements 31′ and 31″ is pressed.

While the invention has been described by way of example and in terms ofthe preferred embodiment(s), it is to the underneath of stood that theinvention is not limited thereto. On the contrary, it is intended tocover various modifications and similar arrangements and procedures, andthe scope of the appended claims therefore should be accorded thebroadest interpretation so as to encompass all such modifications andsimilar arrangements and procedures.

What is claimed is:
 1. A key structure, comprising: a key cap; asupporting board; a bridge assembly disposed between the key cap and thesupporting board, wherein the bridge assembly comprises: a first hingepart, having a first pivot coupling portion; and a second hinge part,having a second pivot coupling portion; a first supporting part and asecond supporting part coupled to two ends of the first pivot couplingportion and two ends of the second pivot coupling portion, respectively,wherein the first supporting part and the second supporting part aredisposed on the supporting board, a material of the first supportingpart is different from a material of the supporting board, and amaterial of the second supporting part is different from the material ofthe supporting board; an attractable element disposed on the secondhinge part; and a magnet correspondingly located under the attractableelement.
 2. The key structure according to claim 1, wherein the magnethas an upper surface, and the attractable element has a lower surfacefacing the upper surface and forming an included angle with the uppersurface when the attractable element has a line contact with the magnet.3. The key structure according to claim 1, wherein the attractableelement has a middle portion between the first end and the second end,the middle portion has a lower surface facing the upper surface inparallel and the lower surface of the middle portion separates a gapfrom the upper surface, the first end of the attractable element has alower surface facing the upper surface and the lower surface of thefirst end contacts the upper surface at an acute angle, and the lowersurface of the first end forms an obtuse angle with the lower surface ofthe middle portion.
 4. The key structure according to claim 2, whereinthe attractable element has an opening, and the opening overlaps theupper surface of the magnet in a vertical projecting direction of thekey cap.
 5. The key structure according to claim 4, wherein theattractable element further comprises a tongue plate extending into theopening and forming another included angle with the upper surface whenthe attractable element has the line contact with the magnet.
 6. The keystructure according to claim 1, wherein the first supporting partcomprises two first pivot holes, the second supporting part comprisestwo second pivot holes, and the two first pivot holes are opposite tothe two second pivot holes for receiving the two ends of the first pivotcoupling portion and the two ends of the second pivot coupling portion,respectively.
 7. The key structure according to claim 6, wherein thefirst supporting part further comprises a positioning hole locatedbetween the two first pivot holes, and the first hinge part has at leasta positioning stick on the axis and received in the positioning hole,wherein when the key cap is pressed to move downwards, the positioningstick has a degree of freedom with respect to the positioning hole in amovement direction of the key cap.
 8. The key structure according toclaim 1, further comprising two first gaskets and two second gaskets,wherein the first gaskets are disposed on the two ends of the firstpivot coupling portion respectively so that the first hinge part and thefirst supporting part and the first hinge part and the second supportingpart are spaced apart at a first distance respectively, and the secondgaskets are disposed on the two ends of the second pivot couplingportion respectively so that the second hinge part and the firstsupporting part and the second hinge part and the second supporting partare spaced apart at a second distance respectively.
 9. The key structureaccording to claim 1, further comprising a thin film circuit boardcorrespondingly located under the bridge assembly, wherein the firsthinge part and the second hinge part further comprise a first protrusionand a second protrusion respectively for being in contact with the thinfilm circuit board, and wherein when the first hinge part and the secondhinge part rotate with respect to each other, the first protrusion andthe second protrusion reduce a tolerance between the first hinge partand the thin film circuit board and a tolerance between the second hingepart and the thin film circuit board respectively.
 10. The key structureaccording to claim 1, wherein the first and second supporting parts arein parallel and erected on the supporting board.
 11. The key structureaccording to claim 10, further comprising a base board, wherein the baseboard stacks with the supporting board, and the base board has a recessfor receiving the magnet, wherein a bottom of the magnet is in contactwith the base board and the magnet is encompassed by sidewalls of therecess.
 12. The key structure according to claim 9, wherein the thinfilm circuit board has a first switch element and a second switchelement, the first hinge part has a first actuation portioncorrespondingly located above the first switch element, the second hingepart has a second actuation portion correspondingly located above thesecond switch element, and the first actuation portion and the secondactuation portion are adjacent to edges of the key cap.
 13. The keystructure according to claim 12, wherein the first switch element aretwo, and the second switch element are two, and the positions of thefirst switch elements and the second switch elements are correspondingto four corners of the key cap.
 14. The key structure according to claim1, wherein the first hinge part further comprises a first connectingportion and the second hinge part further comprises a second connectingportion, the first connecting portion and the second connecting portionare connected to form an axis, and the first hinge part and the secondhinge part rotate with respect to the axis, and the axis is locatedbetween the first pivot coupling portion and the second pivot couplingportion.
 15. The key structure according to claim 14, wherein theattractable element is rotated with the second hinge part in a samerotating direction around the axis.
 16. The key structure according toclaim 1, wherein the attractable element contacts the magnet when thekey cap is not pressed.